要测试OnTermination过渡，可以使用在测试类中扩展TestFSMRef实例的OnTermination方法的方式。例如，假设有一个FSM Actor定义如下：

public class MyFsmActor : FSM
{
    public MyFsmActor()
    {
        StartWith(MyFsmActorState.Idle, Uninitialized);

        When(MyFsmActorState.Idle, @event =>
        {
            if (@event.FsmEvent.Equals("start"))
            {
                Console.WriteLine("Starting...");
                return GoTo(MyFsmActorState.Active);
            }

            return null;
        });

        When(MyFsmActorState.Active, @event =>
        {
            if (@event.FsmEvent.Equals("ping"))
            {
                Console.WriteLine("Pong");
                return null;
            }

            if (@event.FsmEvent.Equals("stop"))
            {
                Console.WriteLine("Stopping...");
                return GoTo(MyFsmActorState.Idle);
            }

            return null;
        });

        OnTransition((state, nextState) =>
        {
            Console.WriteLine($"Transitioning from {state} to {nextState}");
        });

        OnTermination(state =>
        {
            Console.WriteLine($"Terminating {state}");
        });

        Initialize();
    }
}

public enum MyFsmActorState
{
    Idle,
    Active
}

要测试OnTermination过渡，可以考虑以下测试代码：

[TestClass]
public class MyFsmActorTest
{
    [TestMethod]
    public void Test_OnTermination()
    {
        var fsmRef = ActorOfAsTestActorRef();
        fsmRef.Tell("start");
        fsmRef.Tell("ping");

        fsmRef.OnTermination(state =>
        {
            Assert.AreEqual(MyFsmActorState.Active, state);
        });

        fsmRef.Tell(PoisonPill.Instance);

        var isTerminated = fsmRef.WaitUntilTerminated(TimeSpan.FromSeconds(5));
        Assert.IsTrue(isTerminated);
    }
}

该测试代码中，我们创建了一个TestActorRef实例，并使用Tell方法模拟了一些有状态的消息传递。然后，我们扩展了TestActorRef实例的